1. Field of the Invention
This invention relates to a turret punch press with a tapping function.
2. Description of the Prior Art
When forming a female screw by using a tapping process, it is common practice to first form a starting hole in the workpiece by means of a turret punch press or the like before performing the tapping with a tapping machine. However, since this is operationally inefficient, it has become common practice recently to adopt a method in which the tapping operation is performed using a tap 98 mounted on a motor 99 attached to an outer side section of the body MB of a turret punch press, as shown in FIG. 7.
In the case of a punch press which is not of the turret type, it is conventional practice to prepare an optional work set which is composed of a tapping motor 89 and a tap 88, as shown in FIG. 8. This optional work set is mounted on a punch press, tapping being performed on a starting hole which has been previously formed in a tabular workpiece 85 by means of a punch and a die respectively mounted on a punch holder 87 and a die holder 86.
In the conventional method shown in FIG. 7, however, the tapping operation is performed using a turret punch press, so that the tapping motor 99 and the tap 98 must be attached to the punch press at positions clear of the punch turret 97 and the die turret 96. As a result, the tapping motor 99 and the tap 98 are situated well away from the center of punching where the various punching operations such as blanking, boring and drawing are performed, and the workable range available with a single work clamping therefore has to be relatively narrow. It is to be noted that a tapping operation based on the conventional principle must be controlled on a software basis. However, the preparation of the required software is inevitably a rather troublesome task. Furthermore, even when the control is conducted on a software basis, the punching range is discordant with the tapping range, as shown in FIG. 9, since the punching axis is not aligned with the tapping axis, resulting in a reduced available range for working with a single work clamping.
The conventional method illustrated in FIG. 8, according to which the above-described optional work set is mounted on a punch press, does not provide satisfactory operational utility, either, since the central axes of the tapping motor 89 and the tap 88 are inevitably different from those of the punch holder 87 and the die holder 86.
Accordingly, it would be very convenient if a turret punch press could be developed in which punching and tapping can be conducted on one and the same axis.